Let the tutor not merely require a verbal account of what the boy has been taught but the meaning and the substance of it: let him judge how the child has profited from it not from the evidence of his memory but from that of his life. Let him take what the boy has just learned and make him show him dozens of different aspects of it and then apply it to just as many different subjects, in order to find out whether he has really grasped it and make it part of himself, judging the boy's progress by what Plato taught about education. Spewing up food exactly as you have swallowed it is evidence of a failure to digest and assimilate it; the stomach has not done its job if, during concoction, it fails to change the substance and the form of what it is given.